1. Field of the Invention
This present invention is related to a transformer, and more particularly, to an integrated stacked transformer.
2. Description of the Prior Art
Transformer and balun are the important elements in radio frequency integrated circuit to achieve single end to differential conversion, signal coupling, and impedance matching, etc. With integrated circuit developing toward system on chip (SOC), integrated transformer/balun replaces traditional discrete element gradually and is applied in radio frequency integrated circuit widely. However, the passive elements in integrated circuit such like inductor and transformer consume a lot of chip area in general, therefore how to reduce the amount of passive element in integrated circuit and minimize the area of passive element and maximize the specification of element like quality factor Q and coupling coefficient K is an important issue.